Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$51.57	3.643%	$53.4487	$53.45	$53.45	$53.40
Purchase #2	$87.37	11.696%	$97.5888	$97.59	$97.60	$97.60
Purchase #3	$20.27	6.601%	$21.608	$21.61	$21.60	$21.60
Purchase #4	$209.93	9.279%	$229.4094	$229.41	$229.40	$229.40
Purchase #5	$104.63	6.805%	$111.7501	$111.75	$111.75	$111.80
Purchase #6	$92.71	8.724%	$100.798	$100.80	$100.80	$100.80
Purchase #7	$224.80	10.273%	$247.8937	$247.89	$247.90	$247.90
7 purchase totals =	$791.28		$862.4967	$862.50	$862.50	$862.50